Subsea Structure Load Monitoring and Control System

ABSTRACT

A system for monitoring for loads in a subsea structure comprises one or more sensors disposed proximate a subsea structure such as a blow-out preventer. The sensors are configured to detect an induced load on a subsea structure. The detected load is communicated to a sensor data processor operatively in communication with the strain sensor. Using the detected load data, a load generator such as a remotely operated vehicle or other source of thrust has its thrust output adjusted to induce a load equal in force, but opposite in direction, to the detected induced loads.

RELATION TO PRIOR APPLICATIONS

The present application claims priority in part through U.S. Provisional Application 60/950,184 filed Jul. 17, 2007.

FIELD OF THE INVENTION

Loop currents impart loads and deflections onto subsea structures such as blow-out preventors (BOPs) and risers such that the ability to connect and disconnect a BOP to and from a wellhead is hampered. The current may deflect the hanging riser and BOP system away from vertical to a degree that the BOP cannot be latched to the wellhead.

If the BOP is already latched when the current loads are induced, there is no way of knowing what effect those forces will have on the BOP and riser once the connector is unlatched and the BOP is lifted off the connector. If the forces are sufficient, then the current may sweep the BOP and the riser into other equipment installed on the seafloor.

At the current time, drilling operations are halted in strong loop current conditions.

FIGURES

The attached figures illustrate various aspects of exemplary embodiments of the BOP Current Load Monitoring and Control System.

FIG. 1 is an unscaled, side view of a remotely operated vehicle which has engaged a subsea structure to which a sensor array has been mounted;

FIG. 2 is an unscaled, side view of a remotely operated vehicle which has been deployed to engage a subsea structure to which a sensor array has been mounted where the subsea structure is veering off of its intended deployment path; and

FIG. 3 is an unscaled, side view of a remotely operated vehicle which has engaged a subsea structure to which a sensor array has been mounted.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In its various embodiments, the subsea structure load monitoring and control system described herein below allows the running of a subsea structure, e.g. a blowout preventer (BOP), in strong loop currents or other induced loads such as current-induced loads or loads induced by lateral displacement of a vessel away from a wellhead. In the following exemplary embodiments, a system for monitoring loads in such structures, e.g. BOP connectors or risers, allows induced loads such as environmentally induced loads resulting from currents, vessel drift, and the like, or a combination thereof to be monitored and, once the loads are known, counteracted by inducing equal forces in the opposite direction.

Referring now to FIG. 1, one or more sensors 20 is placed proximate a subsea structure, e.g. BOP connector 11, preferably radially. When subsea structure 10 is connected with no induced loads, sensors 20 simply measure the loads that are due to internal, normally-seen connector forces. However, once subsea structure 10 is subjected to a lateral load, sensors 20 will detect additional shear and bending loads superimposed upon the normal loads. Sensors 20 are typically strain sensors such as foil strain gauges manufactured by Vishay Intertechnology, Inc. of Malvern, Pa. or fiber optic strain gauges manufactured by Micron Optics Inc. of Atlanta, Ga.

Sensors 20 interface with and are read by appropriate sensor electronics 22. Sensor electronics 22 may be located on subsea structure 10, lower marine riser package 14, a remotely operated vehicle (ROV) 12, a thruster package (not shown in the figures), or the like, or a combination thereof. In any embodiment, load information obtained from sensors 20 is used to adjust the thrust output of ROV 12 or a thruster package so as to induce a load equal in force, but opposite in direction, to the induced loads such as current-induced loads.

In the operation of a preferred embodiment, referring now to FIG. 2, currents, e.g. water currents, apply force on subsea structures such as subsea structure 10, causing subsea structure 10 to move off of desired path 30. ROV 12 is positioned to interface with coupler 5.

Referring now to FIG. 3, once ROV 12 has mated to coupler 5, sensors 20 detect additional shear and bending loads on subsea structure 10. Sensor electronics 22 communicates with ROV 12, which then applies appropriate counter-forces to move subsea structure 10 back onto desired path 30.

Once the current load and the externally applied counter-force have been applied, an operator can release subsea structure connector 11 and raise subsea structure 10 off of the wellhead without fear of subsea structure 10 or its associated riser, if any, being swept into other equipment. For example, subsea structure 10 may stay vertical during the release and raise operation.

The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or a illustrative method may be made without departing from the spirit of the invention. 

1. A system for monitoring for loads in a subsea structure, comprising: a. a sensor disposed proximate a subsea structure, the sensor configured to detect an induced load on a subsea structure; and b. a sensor data processor operatively in communication with the strain sensor.
 2. The system of claim 1, wherein the induced load is at least one of a current-induced load or a load induced by lateral displacement of a vessel.
 3. The system of claim 1, wherein the sensor comprises a strain sensor.
 4. The system of claim 1, further comprising a load generator operatively in communication with the sensor data processor, the load generator operative to exert a force on the subsea structure in a direction opposed to a direction of a force detected by the strain sensor and in proportion to a load sensed by the strain sensor.
 5. The system of claim 4, wherein the load generator is selected from the group of load generators consisting of a remotely operated vehicle or a thrust package.
 6. The system of claim 1, wherein the sensor is a plurality of operatively interconnected strain sensors.
 7. The system of claim 6, wherein the plurality of strain sensors are disposed radially about the subsea structure.
 8. A method of monitoring and counteracting subsea environmentally induced loads, comprising: a. deploying a strain sensor proximate a subsea structure; b. detecting an induced load on the subsea structure; c. communicating the detected induced load to a load processor; and d. using the detected load data to adjust thrust output of the load generator to induce a load equal in force, but opposite in direction, to the detected induced loads.
 9. The method of claim 8, wherein the induced load is selected from the group of induced loads comprising a current-induced load or a load induced by lateral displacement of a vessel away from a wellhead. 